Tag : Fluctuations

Washington: Rapid changes in marine oxygen levels may have played a significant role in driving Earth's first mass extinction, according to a new study led by Florida State University researchers. About 443 million years ago, life on Earth was undergoing the Late Ordovician mass extinction, or LOME, which eliminated about 85% of marine species. Scientists have long studied this mass extinction and continue to investigate its possible causes, such as reduced habitat loss in a rapidly cooling world or persistent low-oxygen conditions in the oceans. By measuring isotopes of the element thallium, which shows special sensitivity to changes in oxygen in the ancient marine environment, the research team found that previously documented patterns of this mass extinction coincided with an initial rapid decrease in marine oxygen levels followed by a rapid increase in oxygen. Their work is published online in the journal Science Advances. "Paleontologists have noted that there were several groups of organisms, such as graptolites and brachiopods that started to decline very early in this mass extinction interval, but we didn't really have any good evidence of an environmental or climate signature to tie that early decline of these groups to a particular mechanism," said co-author Seth Young, an associate professor in the Department of Earth, Ocean and Atmospheric Science. "This paper can directly link that early phase of extinction to changes in oxygen. We see a marked change in thallium isotopes at the same time these organisms start their steady decline into the main phase of the mass extinction event," he said. That decrease in oxygen was immediately followed by an increase. This rapid shift in oxygen coincided with the traditional first d ...